Direct positive silver halide emulsions
containing halogenated derivatives
of cyanine dyes

ABSTRACT

21. A FOGGED DIRECT POSITIVE SILVER HALIDE EMULSION CONTAINING, AS ELECTRON ACCEPTOR, A CYANIDE DYE DERIVATIVE IN WHICH AT LEAST ONE TERMINAL METHINE GROUP OF THE PARENT CYANINE DYE IS HALOGENATED WITH CHLORINE, BROMINE OR IODINE.

United States Patent 28,258 DIRECT POSITIVE SILVER HALIDE EMULSIONSCONTAINING HALOGENATED DERIVATIVES 0F CYANINE DYES Paul B. Gilman,Rochester, N.Y., Roberta A. Litzerman, Brighton, Mass, and Bernard D.Illingsworth, deceased, late of Rochester, N.Y., by Mary D. Clark,executrix, Rochester, N.Y., assignors to Eastman Kodak Company,Rochester, N.Y.

No Drawing. Original No. 3,501,309, dated Mar. 17, 1970,

Ser. No. 609,734, Jan. 17, 1967, which is a continuation-in-part ofabandoned application Ser. No. 533,458, Mar. 11, 1966. Application forreissue Mar. 16, 1972, Ser. No. 235,394

Int. Cl. G03c N36 US. Cl. 96-101 24 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE Halogenated derivatives of cyanine dyes areincorporated in direct positive emulsions as electron acceptors.

This application is a continuation-in-part of our US. patent applicationSer. No. 533,458, filed Mar. 11, 1966, now abandoned.

This invention relates to photographic emulsions, and more particularlyto novel emulsions featuring certain electron acceptors.

Various compounds have been suggested as electron acceptors forphotographic silver halide emulsions. It is desirable to incorporateelectron acceptors in certain emulsions, such as fogged emulsions, toprovide direct positive images. In this invention, novel emulsions areprovided which feature a class of especially effective electronacceptors. One of the features of the electron acceptors employed inthis invention is that they may be used alone or in combination withspectral sensitizing dyes to extend the response of direct positiveemulsions to radiation having a wave length longer than about 480 mAnother feature of these electron acceptors is that they may beeffectively used in fogged emulsions to provide direct positive imagesof especially good quality, particularly with respect to the absence ofany negative image in the areas of high exposure.

One object of this invention is to provide novel photographic emulsionscontaining certain highly effective electron acceptors. Another objectof this invention is to provide novel, direct positive emulsionsfeaturing a certain class of electron acceptors which may be used withspectral sensitizing dyes. Still another object of this invention is toprovide novel, direct positive emulsions containing certain electronacceptors, which emulsions produce images essentially free of density inareas of high exposure. These and other objects of this invention willbe apparent from this disclosure and the appended claims.

In one embodiment of this invention, silver halide emulsions areprovided which feature, as electron acceptor, a cyanine dye derivativein which at least one terminal methine group of the cyanine dye ishalogenated with chlorine, bromine or iodine. [having at least onemethine group wherein a hydrogen atom thereof is replaced with a halogenatom selected from the group consisting of chlorine, bromine and iodine.A carbon atom linking the two nuclei of the dye can carry one or twohalogen atoms] An especially useful class of electron acceptors [has]are halogenated derivatives of cyanine dyes having the following generalformula:

Re. 28,258 Re issued Dec. 3, 1974 wherein Z and Z each represents thenon-metallic atoms necessary to complete a heterocyclic nucleus of thetype used in cyanine dyes, such as a nucleus containing 5 to 6 atoms,and which may include a hetero atom selected from the group consistingof oxygen, sulfur, nitrogen and selenium, e.g., a nucleus of thebenzothiazole series (e.g., benzothiazole, 4-chlorobenzothiazole,S-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, 5-methylbenzothiazole, S-bromobenzothiazole, 4-phenylbenzothiazole,S-phenylbenzothiazole, G-phenylbenzothiazole, 4-methoxybenzothiazole,S-methoxybenzothiazole, 5-iodobenzothiazole, 4-ethoxybenzothiazole,S-ethoxybenzothiazole, S-hydroxybenzothiazole, etc.); thenaphthothiazole series (e.g. a-naphthothiazole, B-naphthothiazole,S-methoxy-fl-naphthothiazole, S-ethyl-fl-naphthothiazole,S-methoxy-ut-naphthothiazole, 7-methoxy a naphthothiazole, etc); thoseof the benzoxazole series (e.g., benzoxazole, 5- chlorobenzoxazole,S-methylbenzoxazole, S-phenylbenzoxazole, S-methoxybenzoxazole,S-ethoxybenzoxazole, S-hydroxybenzoxazole, etc); those of thenaphthoxazole series (e.g., a-naphthoxazole, fl-naphthoxazole, etc.those of the benzoselenazole series (e.g., benzoselenazole,S-chlorobenzoselenazole, 5 methylbenzoselenazoleS-hydroxybenzoselenazole, etc); those of the naphthoselenazole series(e.g., rat-naphthoselenazole, fl-naphthoselenazole, etc.); those of thequinoline series including the 2-quinolines (e.g., quinoline,3-methylquinoline, S-methylquinoline, 7- methylquinoline,8rnethylquinoline, 6chloroquinoline, 8- chloroquinoline,6-methoxyquinoline, 6-hydroxyquinoline, S-hydroxyquinoline, etc); the4-quinoline (e.g., quinoline, fi-methoxyquinoline, 7-methoxyquinoline,S-methoxyquinoline, etc.); those of the isoquinoline series (e.g., thelisoquinolines, the 3-isoquinolines, etc.); L represents a mcthine group(substituted or unsubstituted, e.g. =CH, =CCH etc.); X and X eachrepresents [an atom selected from the group consisting of] hydrogen,chlorine, bromine and iodine, at least one of X and X being chlorine,bromine or iodine]; R and R each represents an alkyl substituent, e.g.,a lower alkyl group such as methyl, ethyl, propyl, isopropyl, butyl,secondary butyl, tertiary butyl, etc., a sulfoalkyl group in which thealkyl group has from 1 to 4 carbon atoms, such as sulfomethyl,sulfoethyl, sulfopropyl, sulfobutyl, etc, and a carboxyalkyl group inwhich the alkyl group has from 1 to 4 carbon atoms such ascarboxymethyl, carboxyethyl, carboxypropyl, carboxybutyl, etc.; Arepresents an acid anion such as chloride, bromide, iodide,p-toluenesulfonate, thiocyanate, methyl sulfate, ethyl sulfate,perchlorate, and the like; and d, m, n and p each represents a positiveinteger of from 1 to 2.

Advantageously, the novel emulsions of this invention which feature thespecial electron acceptors described above are fogged, direct positiveemulsions. The fogging may be accomplished in any convenient manner,such as with a light exposure or using various chemicals. In a preferredembodiment, the emulsions are fogged with reducing agent and a compoundof a metal more electropositive than silver.

In another embodiment of this invention, the halo genated dyes describedabove are added to an emulsion which comprises silver halide grainshaving a central core of a water-insoluble silver salt containingcenters which promote the deposition of phototolytic silver, and anouter shell covering said core comprising a fogged water-insolublesilver salt that develops to silver without exposure.

The electron acceptors employed in this invention may be prepared byhalogenating a cyanine dye with chlorine, bromine or iodine. Anysuitable halogenating agent may be used, such as aqueous alcoholic(e.g., methanol or ethanol) solutions of the halogen,N-chlorosuccinimide, N-bromosuccinimide, N-iodosuccinimide, or acommercially available halogen-pyrrolidone complex, such as thebromine-pyrrolidone complex sold by General Aniline and Film Corp.[Using such halogenating agents causes relacement by halogen of ahydrogen atom in the methine chain.] In carbocyanines, ordicarbocyanines, it is probable that [halogen substitution] halogenationoccurs on the terminal carbon atoms of the methine chain.

In accordance with one aspect of the invention, novel and improveddirect positive photographic silver halide emulsions are prepared byincorporating one or more of the halogenated cyanine dyes of theinvention into a suitable fogged silver halide emulsion. The emulsioncan be fogged in any suitable manner, such as by light or with chemicalfogging agents, e.g., stannous chloride, formaldehyde, thiourea dioxideand the like. The emulsion may be fogged by the addition thereto of areducing agent such as thiourea dioxide and a compound of a metal moreelectropositive than silver such as a gold salt, for example,

potassium chloroaurate, as described in British Patent 723,019 (1955).

Typical reducing agents that are useful in providing such emulsionsinclude stannous salts, e.g., stannous chloride, hydrazine, sulfurcompounds such as thiourea dioxide, phosphonium salts such astetra(hydroxymethyl) phosphonium chloride, and the like. Typical usefulmetal compounds, that are more electropositive than silver include gold,rhodium, platinum, palladium, iridium, etc., preferably in the form ofsoluble salts thereof, e.g., potassium chloroaurate, auric chloride(NHQ- PdCl and the like.

Useful concentrations of reducing agent and metal compound (e.g., metalsalt) can be varied over a considerable range. As a general guideline,good results are obtained using about .05 to 40 mg. reducing agent permole of silver halide, and 0.5 to 15.0 mg. metal compound per mole ofsilver halide. Best results are obtained at lower concentration levelsof both reducing agent and metal compound.

The concentration of added halogenated dye can vary widely, e.g., fromabout 50 to 2000 mg. and preferably from about 400 to 800 mg. per moleof silver halide in the direct positive emulsions.

As used herein, and in the appended claims, fogged" refers to emulsionscontaining silver halide grains which produce a density of at least 0.5when developed, without exposure, for minutes at 68 F. in developerKodak DK-50 having the composition set forth below, when the emulsion iscoated at a silver coverage of 50 mg. to 500 mg. per square foot.

DEVELOPER G. N-methyl-p-aminophenol sulfate 2.5 Sodium sulfite(anhydrous) 30.0 Hydroquinone 2.5 Sodium metaborate 10.0 Potassiumbromide 0.5

Water to make 1.0 liter.

The halogenated dyes of this invention are also advantageouslyincorporated in direct positive emulsions of the type in which a silverhalide grain has a water-insoluble silver salt center and an outer shellcomposed of a fogged water-insoluble silver salt that develops to silverwithout exposure. The halogenated dyes of the invention areincorporated, preferably in the outer shell of such emulsions. Theseemulsions can be prepared in various ways, such as those described inBerriman US. patent application Ser. No. 448,467, filed Apr. 15, 1965,now US. Patent No. 3,367,778. For example, the shell of the grains insuch emulsions may be prepared by precipitating over the core grains alight-sensitive water-insoluble silver salt that can be fogged and whichfog is removable by bleaching. The shell is of sufficient thickness toprevent access of the developer used in processing the emulsions of theinvention to the core. The silver salt shell is surface fogged to makedevelopable to metallic silver with conventional surface imagedeveloping compositions. The silver salt of the shell is sufiicientlyfogged to produce a density of at least about 0.5 when developed for 6minutes at 68 F. in Developer A below when the emulsion is coated at asilver coverage of mg. per square foot. Such fogging can be effected bychemically sensitizing to fog with the sensitizing agents described forchemically sensitizing the core emulsion, high intensity light and thelike fogging means well known to those skilled in the art. While thecore need not be sensitized to fog, the shell is fogged. Fogging bymeans of a reduction sensitizer, a noble metal salt such as gold saltplus a reduction sensitizer, a sulfur sensitizer, high pH and low pAgsilver halide precipitating conditions, and the like can be suitablyutilized. The shell portion of the subject grains can also be coatedprior to fogging.

DEVELOPER A N-methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0Potassium metaborate 35.0 Potassium bromide 1.0 Water to make 1 liter.pH of 9.6.

Before the shell of water-insoluble silver salt is added to the silversalt core, the core emulsion is first chemically or physically treatedby methods previously described in the prior art to produce centerswhich promote the deposition of photolytic silver, i.e., latent imagenucleating centers. Such centers can be obtained by various techniquesas described herein. Chemical sensitization techniques of the typedescribed by Antoine Hautot and Henri Saubeneir in Science et IndustriesPhotographiques, vol. )OWIII, January 1957, pages 1 to 23 and Jaunary1957, pages 57 to 65 are particularly useful. Such chemicalsensitization includes three major classes, namely, gold or noble metalsensitization, sulfur sensitization, such as by a labile sulfurcompound, and reduction sensitization, e.g., treatment of the silverhalide with a strong reducing agent which introduces small specks ofmetallic silver into the silver salt crystal or grain.

The halogenated dyes of this invention are highly useful electronacceptors in high speed direct positive emulsions comprising foggedsilver halide grains and a compound which accepts electrons, asdescribed and claimed in Illingsworth US. patent application Ser. No.609,794 filed Jan. 17, 1967 now abandoned and continuation-inpart Ser.No. 619,936 filed Mar. 2, 1967 and titled Photographic ReversalMaterials III." The fogged silver halide grains of such emulsions aresuch that a test portion thereof, when coated as a photographic silverhalide emulsion on a support to give a maximum density of at least aboutone upon processing for six minutes at about 68 F. in Kodak DK-SOdeveloper, has a maximum density which is at least about 30% greaterthan the maximum density of an identical coated test portion which isprocessed for six minutes at about 68 F. in Kodak DK-50 developer afterbeing bleached for about 10 minutes at about 68 F. in a bleachcomposition of:

Potassium cyanide mg 50 Acetic acid (glacial) cc 3.47 Sodium acetate t g11.49 Potassium bromide mg 119 Water to make 1 liter.

The grains of such emulsions will lose at least about and generally atleast about 40% of their fog when bleached for ten minutes at 68 F. in apotassium cyanide bleach composition as described herein. This fog losscan be illustrated by coating the silver halide grains as a photographicsilver halide emulsion on a support to give a maximum density of atleast 1.0 upon processing for six minutes at about 68 F. in Kodak DK-SOdeveloper and comparing the density of such a coating with an identicalcoating which is processed for six minutes at 68 F. in Kodak DK-SOdeveloper after being bleached for about 10 minutes at 68 F. in thepotassium cyanide bleach composition. As already indicated, the maximumdensity of the unbleached coating will be at least greater, generally atleast 60% greater, than the maximum density of the bleached coating.

The silver halides employed in the preparation of the photographicemulsions useful herein include any of the photographic silver halidesas exemplified by silver bromide, silver iodide, silver chloride, silverchlorobromide,

silver bromoiodide, silver chlorobromide, and the like. Silver halidegrains having an average grain size less than about one micron,preferably less than about 0.5 micron, give particularly good results.The silver halide grains can be regular and can be any suitable shapesuch as cubic or octahedral, as described and claimed in IllingsworthU.S. patent application Ser. No. 609,778 filed Jan. 17, 1967 nowabandoned, and continuation-impart 619,909 filed Mar. 2, 1967 and titledDirect Positive Photographic Emulsion I." Such grains advantageouslyhave a rather uniform diameter frequency distribution, as described andclaimed in Illingsworth U.S. patent application Ser. No. 609,790 filedJan. 17, 1967 now abandoned, and continuation-in-part Ser. No. 619,948filed Mar. 2, 1967 and titled Photographic Reversal Emulsions II. Forexample, at least 95%, by weight, of the photographic silver halidegrains can have a diameter which is within about preferably within about30% of the mean grain diameter. Mean grain diameter, i.e., average grainsize, can be determined using conventional methods, e.g., as shown in anarticle by Trivelli and Smith entitled Empirical Relations BetweenSensitometric and Size-Frequency Characteristics in PhotographicEmulsion Series in The Photographic Journal, vol. LXXIX, 1949', pages330-338. The fogged silver halide grains in these directpositivephotographic emulsions of this invention produce a density of at least0.5 when developed without exposure for five minutes at 68 F. in KodakDK developer when such an emulsion is coated at a coverage of 50 toabout 500 mg. of silver per square foot of support. The preferredphotographic silver halide emulsions comprise at least 50 mole percentbromide, the most preferred emulsions being silver bromoiodideemulsions, particularly those containing less than about ten molepercent iodide. The photographic silver halides can be coated at silvercoverages in the range of about 50 to about 500 milligrams of silver persquare foot of support.

In the preparation of the above photographic emulsions, the halogenateddyes of the invention are advantageously incorporated in the washed,finished silver halide emulsion and should, of course, be uniformlydistributed throughout the emulsion. The methods of incorporatinghalogenated dyes and other addenda in emulsions are relatively simpleand well known to those skilled in the art of emulsion making. Forexample, it is convenient to add them from solutions in appropriatesolvents, in which case the solvent selected should be completely freefrom any deleterious effect on the ultimate light-sensitive materials.Methanol, isopropanol, pyridine, water, etc., alone or in admixtures,have proven satisfactory as solvents for this purpose. The type ofsilver halide emulsions that can be sensitized with the new halogenateddyes include any of those prepared with hydrophilic colloids that areknown to be satisfactory for dispersing silver halides, for example,emulsions comprising natural materials such as gelatin, albumin,agar-agar, gum arabic, alginic acid, etc, and hydrophilic syntheticresins such as polyvinyl alcohol, polyvinyl pyrrolidone, celluloseethers, partially hydrolyzed cellulose acetate, and the like.

The halogenated dyes, reducing agents and metal compounds of theinvention can be used with emulsions prepared, as indicated above, anyof the light-sensitive silver halide salts including silver chloride,silver bromide, silver chlorobromide, silver bromoiodide, silverchlorobromoiodide, etc. Particularly useful for direct positive foggedemulsions in which the silver salt is a silver bromohalide comprisingmore than 50 mole percent bromide. The halogenated dyes of thisinvention are also useful in emulsions which contain color formers.

The novel emulsions of this invention may be coated on any suitablephotographic support, such as glass, film base such as celluloseacetate, cellulose acetate butyrate, polyesters such as polyethyleneterephthalate, paper, baryta coated paper, polyolefin coated paper,e.g., polyethylene or polypropylene coated paper, which may be electronbombarded to promote emulsion adhesion, to produce the novelphotographic elements of the invention.

This invention will be further illustrated by the following examples.Examples 1 and 2 show preparation of direct positive emulsions by lightfogging and adding the special electron acceptors of the invention.

Example 1 To 40 ml. of solution of ethyl alcohol containing 5x10 gramsof the sensitizing dye, 1,1'-diethyl-2,2'- cyanine chloride is added 20ml. of an aqueous solution containing 2 10- grams of abromine-pyrrolidone complex sold by the General Aniline and Film Corp.The mixture of these two solutions results in the conversion of thepreviously red colored solution by the dye (absorption max-540 m to ablue colored solution (absorption max590 mi). The blue form of the dyeis light sensitive and should be prepared and used only in totaldarkness to prevent spontaneous decomposition. To evaluate the directpositive producing property of [this blue form of] the halogenated dyeon a gelatino silver halide emulsion, a silver chlorobromide emulsion(halide content: 60 mole percent bromide. 40 mole percent chloride) wascoated on a support at 250 mg. per square foot silver and 500 mg. persquare foot gelatin. This film was exposed through a step wedge andimmersed in the solution prepared as the above described blue dye for 2minutes. After drying the layer in the dark, a second exposure wasgiven. The emulsion was immersed for 1 minute in Kodak developer D-72 at20 C. and fixed. In the areas of the emulsion which received the secondexposure, the ellect of the first exposure was removed. When theemulsion was uniformly fogged before the dye treatment. a directpositive image was obtained with the second exposure. The emulsion wassensitive to radiation of 480 to 600 me with maximum sensitivity at 590m No reversal images were obtained when the unbrominated dye wasemployed in ethyl alcohol solution, or when the brominepyrrolidonecomplex was employed in the ethanol solution.

EXAMPLE 2 The film of Example 1 is exposed and processed as in Example 1except that the dye employed is 1',3-diethylthia-2'-cyanine iodide (itis halogenated in the same manner as in Example 1). Similar results areobtained.

A series of halogenated dyes were prepared by the dropwise addition of asolution of 8 mg. N-bromosuccinimide (NBS) per ml. methanol to amethanolic solution of cyanine dye (8 mg. dye in 15 cc. methanol), untilno further color change occurred. [At least one hydrogen atom in themethine chain of the dye is replaced with a bromine atom] The dyes usedare listed below, together with the number of equivalents NBS employed:

(N) 1,1'-dimethyl-2,2'-cyanine iodide, 3 NBS (the car- 1 bon atomsjoining the two quinoline rings of this dye carry two bromine atoms)l-ethyl-l'-methyl-2,2'-cyanine iodide, 3 NBS (P)l,3-dimethylthia-2'-cyanine iodide, 2 NBS (Q)l'-ethyl-2-methylthia-2'-cyanine iodide, 2 NBS (R)I'-methyl-3-ethylthia-2'-cyanine iodide, 2 NBS (S)l,3-diethylthia-2'-cyanine iodide, 2 NBS (T)3-ethyl-3'-methylthiacyanine iodide, 2 NBS Other dyes used forcomparison purposes in the following examples, are listed below.

(I) l,1',3,3'-tetramethyl-2,2-cyanine iodide (II)3,3'-diethylthiacyanine iodide (III) 3,3'-diethylthiacarbocyanine iodide(IV) 3,3'-diethylthiadicarbocyanine iodide (V)3,3'-diethylthiatricarbocyanine iodide (VI)3,3'-diethyl-9-methylthiacarbocyanine bromide (VII)9-ethyl-3,3'-dimethyl-4,5,4',5'-dibenzothiacarbocyanine chloride (VIII)l,l'-diethyl 2,2'-cyanine chloride (IX)Anhydro-9-ethyl-3,3'-di(3-sulfopropyl)-4,5,4',5'-

dibenzothiacarbocyanine hydroxide, sodium salt (X)3,3'-dimethyl-8,l0-di(m-toloxy)thiacarbocyanine bromide (XI)l,3-diethylthia-2'-cyanine iodide (XII) 4- 1-ethyl-2(1H)-fl-naphthothiazolylidene)isopropylidene]-3-methyl-l-(P-sulfophenyl)-5-pyrazolone (XIII)Anhydro-9-ethyl-5,5'-diphenyl-3,3-di(3-sulfobutyl)-oxacarbocyaninehydroxide, monosodium salt (XIV)Anhydro-5,5',6,6'-tetrachloro-l,l'-diethyl-3,3'-di3-sulfobutyl)benzimidazolocarbocyanine hydroxide (J)S-m-nitrobenzylidenerhod anine (L) Phenosafranin.

The following examples illustrate the use of halogenated cyanine dyes inchemically fogged emulsions. In these examples, the concentration of thehalogenated dye is based on the weight of the dye before reaction withNBS. Example 3 shows that direct positive images are obtained withfogged emulsions containing halogenated cyanine dyes, but not with thecorresponding cyanine dyes which have not been halogenated.

Example 3 A gelatin silver bromide emulsion was reduction-gold fogged byfirst adding 0.2 mg. of thiourea dioxide per mole of silver and heatingfor 60 minutes at 60 C. and then adding 0.4 mg. of potassiumchloroaurate per mole of silver and heating for 60 minutes at 65 C. Theemulsion was melted at 40 C. and split into portions to which thefollowing electron acceptors or brominated dyes dissolved in appropriatesolvents were added. The emulsions were coated on cellulose acetate filmsupport (silver coverage 257 mg. per square foot; gelatin coverage 392mg. per square foot), chill-set and dried. The films were exposed on anEastman sensitometer type 13 to light from a tungsten source modulatedby a continuous wedge, developed for minutes in Kodak developer DK-SO at8 20 C., fixed, washed and dried. The following results were obtained:

Bruminatcd Dye (cone. gJmole of silver halide) Density In unexposedarea.

0. 92 0. I 0. 82 0. 06 0. 79 0. l2 0. 5 0. 26 0. 7 D. 09 0. 3 0. I2 0.36 0. l4 1. 26 0, 06

Dye (cone. g./ mole silver halide): Description of results I (0.2) Noreversal-negative image. II (0.2 Do. In 0.2 Do. IV (0.2) Do. V (0.2) Do.VI (0.2) Do. VII (0.2) Do. VIII (0.2) Do.

The inactivity of N-bromosuccinimide in gelatino silver halide emulsionsfogged, exposed and processed as in Example 3 described above is shownbelow.

Unsensitized control Type of Addendum (cone. g./mole Description ofemulsion silver halide) results Bromide None No reversal, negative imageonly. Do. N-bromosuccininilde (.008). Do. Do N-hromosuccinlmide (.l96)Do. Chlorohrolnlde. None Do. Do N-bromosueclnimlde (.4) Do.

Example 4 establishes that logged direct positive emulsions containingthe halogenated dyes of the invention may be spectrally sensitized witha suitable spectral sensitizing dye.

Example 4 Election acceptor Density Wratten No. (cone. g./ in 16 filtermin. mole sllver sensitizing dye (cone. unexposed den. In hallde)g./mole silver halide) area exposed area None one 1.16 No reversal.

Do IX (0.2) 0.38 Do.

Do X (0.2) 0.70 Do.

Do VIIIX(it%8?5)+XI (.0875)+ 0.83 Do.

Do XIII (0.1)-l-XIV (0.1)..- 107 Do. I (0.1) None 0.80 Do. K (0. 0. 9Do. J (0 0.74 Do. K (0. 0. 82 0.16. 1(0. 0.40 0.21. K (0. 0. 70 0.19. J(0. g 0.66 0.20.

XII (.025). K (0.2) VIII (.0875H-XI (.0875H- 0. 96 0.24.

XII (.025).

J (0.2). XIII (tLlH-XIV (0.1)"-.. 0.60 No reversal. K (0.2) XIII(0.1)-l-XIV (0.1).. 0.73 0.37,

Example 5 shows the use of various electron acceptors featured in thisinvention in a fogged silver chlorobromide emulsion.

Example 5 The following data were obtained in the manner described inExample 3, except that the gelatin silver chlorobromide emulsiondescribed in Example 1 was used, and the films were developed for 6minutes in Kodak developer D19 at 20 C. and fixed.

9 Comparison of the data for electron acceptors I and L with those frombrominated sensitizing dyes M through T, K, C and H illustrate thesuperiority of the latter in the system.

Minimum Description 01' Electron acceptor density in response in (none.gJmole Density in exposed areas areas of high silver halide) exposedareas (no filter) exposure level None. (See below) I (0.2) 0.85 0. 62Negative image. J (0.1) 1.07 0.51 Do. L (0.2) 1. 65 0. 78 Do. 11 1.030.07 Minimum density. M (0 1. 11 0. 08 D0. N (0 c 0.88 0.08 Do. 0 (0.0.89 0. 08 D0. P (0. 0.77 0.12 Do. Q (0. 0. 70 0. 21 Do. It (0 0. 63 O.11 D0. S (0. 0.75 0.14 Do. K (0 1. 40 0. 16 Do. '1 (0. 1.00 0. 08 Do. C(0.2) 1. 38 0. 52 D0.

The control shows an increase in density with exposure (negative image)which goes through a maximum and then decreases (solarization). Theemulsions of the invention initially show a decrease in density withexposure. The reversal obtained at high exposure levels with prior artelectron acceptors J and L does not occur with the brominated dyes ofthe invention.

Example 6 The following data were obtained as in Example 3, but usingKodak developer D-19. This example illustrates the superiority ofbrominated dyes in a coarsegrain, gelatin silver bromide, reductionandgold-sensi- Example 7 illustrates direct positive emulsions in which thesilver halide grain has a water-insoluble silver salt center and anouter shell composed of a fogged water insoluble silver salt thatdevelops to silver without exposure, which emulsion features ahalogenated dye in accordance with the invention. Example 7 also showsthe preparation of such emulsions.

Example 7 Silver nitrate and solution chloride solutions were run into asolution of gelatin for 20 minutes at 70 C. The emulsion was cooled and0.2 g. of potassium chloroiridite per silver mole was added. Theemulsion was reheated to 70 C., and more silver nitrate and sodiumchloride were run in for 20 minutes. The emulsion was cooled to 40 C.and fogged by adding 4.0 mg. thiourea dioxide (used to fog the surfaceof the emulsion grains) and 4.0 ml. of 2.5 N sodium hydroxide per moleof silver. The emulsion was acidified and gelatin added to bring thetotal to 160 g. of gelatin per mole of silver. It was then spectrallysensitized by adding 200 mg. of Dye Z per mole of silver. To a portionof the emulsion was added 100 mg. of N per mole of silver. The emulsionswere coated on a cellulose acetate film support at a coverage of 120 mg.silver per square foot, exposed on an Eastman 1B sensitometer, andprocessed for 1 /2 minutes in a developer having the followingcomposition:

Example 8 Coatings were prepared as in Example 7, except that nopotassium chloroiridite was added during precipitation of the emulsion.These results also show the advantage gained by using a brominated dyein combination with a sensitizing dye.

Relative Feature speed mnx, l)|nin,

200 mg. Z/mole silver 0. 66 0. 04 200 mg. Z/mole silver plus 100 m Nmole silver 6, 310 0. 64 0. 01

In Examples 7 and 8, dye Z refers to 3-carboxymethyl- 5[(3-methyl-2-thiazolidinylidene)-l-methylethylidcne] rhodanine.

Other methods for preparing emulsions of the type used in Examples 7 and8 are disclosed and claimed in Berriman U. S. patent application No.448,467, filed Apr. 15, 1965, referred to above.

The emulsions of this invention may be dispersed in any photographichydrophilic colloid, such as any of those referred to in US. Patent3,039,873, column 13, and may contain any of the hardeners orplasticizers referred to in columns 12 and 13 of that patent.

Although the invention has been described in consilerable detail withparticular reference to certain preferred embodiments thereof, it willbe understood that variations and modifications can be eifected withinthe spirit and scope of the invention as described hereinabove, and asdefined in the appended claims.

We claim:

[1. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a halogenated cyanine dye having at least oneterminal methine group wherein the hydrogen atom thereof is replacedwith a halogen atom selected from the group consisting of chlorine,bromine and iodine atoms.

[2. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a cyanine dye having the following general formula:

wherein Z; and Z, each represents the non-metallic atoms necesary tocomplete a heterocyclic nucleus containing from 5 to 6 atoms; Lrepresents a methine group; X and X each represents an atom selectedfrom the group consisting of hydrogen, chlorine, bromine and iodineatoms, at least one of X and X being selected from the gr up consistingof chlorine, bromine and iodine; R and R each represents an alkylsubstituent; A represents an anion; and d, m, n, and p each represents apositive integer of from 1 to 2.]

3. A direct positive emulsion in accordance with claim [1] 23 whereinsaid emulsion is light-fogged and the cyanine dye is a simple cyanine.

4. A direct positive emulsion in accordance with claim [1] 23 whereinthe emulsion is chemically fogged with a reducing agent.

5. A direct positive emulsion in accordance with claim [1] 23 whereinsaid emulsion is sensitized to radiation having wave lengths longer thanabout 480 m with a photographic spectral sensitizing dye.

6. A direct positive emulsion in accordance with claim [2] 23 whereinsaid emulsion comprises grains having a central core of awater-insoluble silver salt containing centers which promote thedeposition of photolytic silver, and an outer shell covering said corecomprising a fogged water-insoluble silver salt that develops to silverwithout exposure.

7. A direct positive emulsion in accordance with claim [2] 23 whereinsaid emulsion is fogged with a reducing agent and a compound of a metalmore electropositive than silver.

[8. A photographic emulsion in accordance with claim 2 wherein said dyeis 1,1,3,3'-tetramethyl-2,2'-cyaninc iodide wherein at least one of thehydrogen atoms of the methine chain thereof is replaced with a bromineatom] [9. A photographic emulsion in accordance with claim 2 whereinsaid dye is 3,3'-diethylthiacyanine iodide wherein at least one of thehydrogen atoms of the methine chain thereof is replaced with a bromineatom] [10. A photographic emulsion in accordance with claim 2 whereinsaid dye is 3,3'-diethylthiacarbocyanine iodide wherein at least one ofthe hydrogen atoms of the methine chain thereof is replaced with abromine atom] [11. A photographic emulsion in accordance with claim 2wherein said dye is 3,3-diethylthiadicarbocyanine iodide wherein atleast one of the hydrogen atoms of the methine chain thereof is replacedwith a bromine atom] [12. A photographic emulsion in accordance withclaim 2 wherein said dye is 9-ethyl-3,3'-dimethyl-4,5,4',5'-dibenzothiacarbocyanine chloride wherein at least one of the hydrogenatoms of the methine chain thereof is replaced with a bromine atom] [13.A photographic emulsion in accordance with claim 2 wherein said dye is1'-methyl-3-ethylthia-2'- cyanine iodide wherein at least one of thehydrogen atoms of the methine chain thereof is replaced with a bromineatom] [14. A photographic emulsion in accordance with claim 2 whereinsaid dye is 1,1'-diethyl-2,2'-cyanine salt wherein the carbon atomjoining the two quinoline rings of said dye carries two bromine atoms]15. A direct positive, photographic emulsion in accordance with claim[I] 21 which comprises fogged silver halide grains, said grains beingsuch that a test portion thereof, when coated as a photographic silverhalide emulsion on a support to give a maximum density of at least about1 upon processing for 6 minutes at about 68 F. in Kodak DK-SO developer,has a maximum density which is at least about greater than the maximumdensity of an identical coated test portion which is processed for 6minutes at about 68 F. in Kodak DK-SO developer after being bleached forabout 10 minutes at about 68 F. in a bleach composition of:

Potassium cyanide mg 50 Acetic acid (glacial) cc 3.47 Sodium acetate g11.49 Potassium bromide mg 119 Water to 1 liter.

16. A direct positive, photographic emulsion in accordance with claim[1] 21 which comprises fogged silver halide grains, at least 95%, byWeight, of said grains having a size which is within about of the meangrain size.

17. A direct positive, photographic emulsion in accordance with claim[2.] 23 which comprises fogged silver halide grains, said grains beingsuch that a test portion thereof, when coatecd as a photographic silverhalide emulsion on a support to give a maximum density of at least about1 upon processing for 6 minutes at about 68 F. in Kodak DK-SO developer,has a maximum density of an identical coated test portion which isprocessed for 6 minutes at about 68 F. in Kodak DK-SO developer afterbeing bleached for about 10 minutes at about 68 F. in a bleachcomposition of:

Potassium cyanide mg 50 Acetic acid (glacial) cc 3.47 Sodium acetate g11.49 Potassium bromide mg 119 Water to 1 liter.

18. A direct positive, photographic emulsion in accordance with claim[2] 23 which comprises fogged silver halide grains, at least by weight,of said grains having a size which is within about 40% of the mean grainsize.

[19. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a simple cyanine dye in which the carbon atom joiningthe nuclei of said dye carries two halogen atoms selected from the groupcon sisting of chlorine, bromine and iodine atoms] [20. A fogged directpositive silver halide emulsion containing, as electron acceptor, asimple cyanine dye in which the carbon atom joining the nuclei of saiddye carries two bromine atoms] 21. A jogged direct positive silverhalide emulsion containing, as electron acceptor, a cyanine dyederivative in which at least one terminal methine group of the parentcyanine dye is halogenated with chlorine, bromine or iodine.

22. A jogged direct positive silver halide emulsion containing, aselectron acceptor, a cyanine dye derivative in which at least oneterminal methine group of the parent cyanine dye is halogenated withchlorine or bromine.

23. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a cyanine dye derivative in which at least oneterminal methine group of the paren! cyanine dye is halogenated withbromine.

24. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a simple cyanine dye derivative in which the methinegroup of the parent cyanine dye is brominated.

25. A jogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is l,1',3,3'-tetramethyl- 2,2'-cyanine iodide.

26. A jogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is 3,3'-diethylthiacyanine iodide.

27. A fogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is 3,3-diethylrhiacarbocyanine iodide.

28. A jogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is 3,3-diethylthiadicarbocyanine iodide.

29. A fogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is 9-erhyl-3,3'-dimethyl-4,5,4',5'-dibenzorhiacarbocyanine chloride.

30. A fogged direct positive emulsion as defined in claim 23 whereinsaid cyanine dye is 1'-merhyl3-ethylthia- 2-cyanine iodide.

31. A fogged direct positive silver halide emulsion containing, aselectron acceptor, a 1,1'-di(lower)alkyl-2,2'- cyanine dye derivative inwhich the methine group of said dye is brominated.

32. A fogged direct positive photographic silver halide emulsioncontaining, as electron acceptor, the reaction product of a brominaringagent with a cyanine dye selected from the group consisting of:

1 ,1 ',3,3'-tetramerhyl-2,2'-cyanine 3,3'-dierhylthiacyanine3,3'-diethylrhiacarbocyanine 3,3 '-dieth ylthiadicarbocyanine3,3'-diethylthiatricarbocyanine 3,3'-diethyl-9-methylthiacarbocyanine9-ethyl-3,3'-dimethyl-4,5,4,5'-dibenzothiacarbocyanine 1 ,1'-diethyl-2,2-cyanine 3,3 '-dimethylthiacyanine 3-br0m0-I,1-diethyl-2,2'-cyanine J-ethyl-l -methyl-2,2-cyanine I ',3-dimethyIthia-2'-cyanine 1'-ethyl-Z-methylthia-2'-cyanine I -methyI-3-ethylthia-2'-cyanine 1',3-diethylthia-2'-cyanine and 3-ethyl-3-metlzylthiacyanine.

33. A jogged direct positive photographic silver halide emulsioncontaining, as electron acceptor, the reaction product of a1,1'-diethyl-2,2-cyanine salt with N-bromosuccinimide.

34. A fogged direct positive silver halide emulsion containing, aselectron acceptor, the reaction product of a cyanine dye with abrominating agent or a chlorinating agent.

35. A fogged direct positive silver halide emulsion containing, aselectron acceptor, the reaction product of a cyanine dye with abrominating agent.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 3,531,290 9/1970 Litzerman 96I08 3,531,288 9/1970Jones 96108 2,111,183 3/1938 Heilbron et a1 96106 X 2,930,694 3/1960Coenen et at. 96105 X 3,367,778 2/1968 Berriman 96-434 FOREIGN PATENTS723,019 2/1953 Great Britain.

DAVID KLEIN, Primary Examiner J. L. GOODROW, Assistant Examiner US. Cl.X.R. 96107, 108

21. A FOGGED DIRECT POSITIVE SILVER HALIDE EMULSION CONTAINING, ASELECTRON ACCEPTOR, A CYANIDE DYE DERIVATIVE IN WHICH AT LEAST ONETERMINAL METHINE GROUP OF THE PARENT CYANINE DYE IS HALOGENATED WITHCHLORINE, BROMINE OR IODINE.